Drugs may be delivered to patients by a variety of methods including oral, intravenous, intramuscular, inhalation, topical or subcutaneous delivery. The drug may be delivered directly or locally to the treatment site (e.g., intrathecally, intraspinally, intraarticularly, etc.). The method of delivery chosen depends upon, among other things, the condition being treated, and the desired therapeutic concentration of the drug to be achieved in the patient and the duration of drug concentration that must be maintained.
Drug pellets, such as, for example, drug depots have been developed, which allow a drug to be introduced or administered to sites beneath the skin of a patient. Drug depot release the drug over a period of time. Drug depots allow the drug to be released from the depot in a relatively uniform dose over weeks, months or even years. Administering drugs using drug depots is becoming especially important and popular in modulating the immune, inflammation and/or pain responses in treatment of chronic conditions including rheumatoid arthritis, osteoarthritis, sciatica, carpal tunnel syndrome, lower back pain, lower extremity pain, upper extremity pain, cancer, tissue pain and pain associated with injury or repair of cervical, thoracic, and/or lumbar vertebrae or intervertebral discs, rotator cuff, articular joint, TMJ, tendons, ligaments, muscles, and the like.
Drug depots are typically inserted into a treatment site beneath the skin of a patient by use of a two-piece device that comprises a cannula or needle and a stylet or plunger that pushes the drug depot through the cannula or needle. The device requires an incision to be made through the skin using a separate instrument (e.g., scalpel). The cannula or needle may be inserted through the incision. The drug depot is inserted through the cannula or needle, and the stylet or plunger is used to push the implant to the end of the cannula or needle. The cannula or needle and stylet or plunger are then withdrawn completely, leaving the drug depot at the implant site.
Typically, the cannula or needle is an epidural Tuohy needle that has a curved tip and a stylet or plunger that comprises a flat tip is used to push the drug depot(s) through the cannula or needle. However, the flat tip of the stylet or plunger limits the amount that the tip can enter the curved tip of the Tuohy needle, thus preventing the stylet or plunger from reaching the opening at the curved end of the Tuohy needle. This may result in one or more drug depots becoming jammed in the curved end of the Tuohy needle, since the stylet or plunger cannot push the drug depots all the way through the Tuohy needle. This disclosure describes an improvement over these prior technologies.